Data transfer control method for controlling transfer of data through a buffer without causing the buffer to become empty or overflow

Abstract

A data transfer control system in a data transfer apparatus including a plurality of data processing units having different data transfer speeds and a temporary holding circuit provided between the data processing units for temporarily holding data transferred between the data processing units. The data transfer apparatus sends a transfer request for data corresponding to a data storage capacity of the temporary holding circuit of the data transfer apparatus to the data processing unit on the side of sending data and sends a transfer request for data corresponding to the data storage capacity of the temporary holding circuit after an elapse of a delivering time of data to an information processing unit on the data transferred side of the temporary holding circuit from the time of the data transfer request is sent until the requested data from the data processing unit on the data sending side reaches the temporary holding circuit of the data transfer apparatus.

We claim: 
     
       1. A data transfer control method for a data transfer apparatus which controls data transfer, through a buffer in said data transfer apparatus, between data processing apparatuses having different data transfer speeds, comprising: a first transfer control step of transmitting data transfer requests from said data transfer apparatus to a first data processing apparatus, which supplies data, so as to transfer an initial quantity of data less than the data storing capacity of said buffer, in predetermined unit amounts, from said first data processing apparatus to said buffer in said data transfer apparatus;   a second transfer control step of transmitting further data transfer requests for a subsequent quantity of data from said data transfer apparatus to said first data processing apparatus to transfer a predetermined unit amount of data each time a sweep-out time has elapsed until data requested by the first transfer control step has arrived at the buffer, said sweep-out time being a time required for receiving and sweeping out a predetermined unit amount of data from said buffer to a second data processing apparatus, which receives data from said buffer, wherein transmitting said further data transfer request after said sweep-out time has elapsed prevents said buffer from ever reaching an empty an overflow condition; and   a third transfer control step of transmitting at least one other data transfer request for transferring predetermined unit amounts of data to said first data processing apparatus, after the data requested by said first transfer control step has arrived at the buffer, and after a predetermined unit amount of data transferred to said buffer has been transmitted from the buffer to the second processing apparatus.   
     
     
       2. A data transfer control method according to claim 1, wherein said sweep out time is determined according to an average data transfer speed from said buffer to said second data processing apparatus. 
     
     
       3. A data transfer control method according to claim 1, wherein said first transfer control step further includes a step of receiving a data transfer start instruction from said first data processing apparatus and receiving information for indicating a total amount of data to be supplied from said first data processing apparatus. 
     
     
       4. A data transfer control method according to claim 3, wherein the sending of a data transfer request to said first data processing apparatus is repeated, until all of the data indicated by said information from said first data processing apparatus has been requested. 
     
     
       5. A data transfer control method according to claim 4, wherein data transfer from said buffer to said second data processing apparatus is monitored and when all of the data indicated by said information is transferred to the second data processing apparatus, a termination of data transfer is communicated to said first data processing apparatus. 
     
     
       6. A data transfer control method for a data transfer apparatus which controls data transfer, through a buffer in said data transfer apparatus, between a higher-rank data processing apparatus, which supplies data, and a lower-rank information recording sub-system, comprising: a first transfer control step of transmitting at least one first data transfer request from said data transfer apparatus to said data processing apparatus, so as to initiate transfer, in predetermined unit amounts, of an initial quantity of data which is less than the data storing capacity of said buffer by less than a predetermined unit amount, from said data processing apparatus to said data transfer apparatus;   a second transfer control step of transmitting at least one second further data transfer request for a subsequent quantity of data from said data transfer apparatus to said data processing apparatus to transfer a predetermined unit amount of data each time a sweep-out time has elapsed until data requested by the first transfer control step hs arrived at the buffer, said sweep out time being the time required for receiving and sweeping out a predetermined unit amount of data from said buffer to the information recording sub-system, which receives data from said buffer, wherein transmitting said second data transfer request after said sweep-out time has elapsed prevents said buffer from ever reaching an empty or overflow condition; and   a third transfer control step of transmitting at least one third data transfer request for transferring predetermined unit amounts of data to said data processing apparatus, after the data requested by said first transfer control step has arrived at the buffer, and after a predetermined unit amount of data transferred to said buffer has been transmitted from the buffer to the information recording sub-system.   
     
     
       7. A data transfer control method according to claim 6, wherein the sweep out time is determined according to an average data transfer speed from said buffer to said information recording sub-system. 
     
     
       8. A data transfer control method according to claim 6, wherein said first transfer control step further includes a step of receiving a data transfer start instruction from said data processing apparatus and receiving information for indicating a total amount of data to be supplied from said data processing apparatus. 
     
     
       9. A data transfer control method according to claim 8, wherein the sending of a data transfer request to said data processing apparatus is repeated, until all of the data indicated by said information from said data processing apparatus has been requested. 
     
     
       10. A data transfer control method according to claim 9, wherein data transfer from said buffer to said information recording sub-system is monitored and when all of the data indicated by said information is transferred to the information recording sub-system, a termination of data transfer is communicated to said data processing apparatus.